Automatic stoker



Jam. 13, 1942. w. M. FULTON 2,269,812

AUTOMATIC STOKER Filed Oct. 9, 1939 13 Sheets-Sheet 1 W. M. FULTON AUTOMATIC STOKER Filed Oct. 9. 1939 13 Sheets-Sheet 3 Fame 11 ior Jan. M, 1942. W.'M. FULTON I AUTOMATIC STOKER Filed Oct. 9, 1939 13 Sheets-Sheet 4 I06 205 Z@?' Z52 Jan, 13, 1942. W. M. FULTON 2,269,812

AUTOMATIC STOKER l3 Sheets-Sheet 5 Filed Oct. 9, 1939 Unve nfl'or Jw M3, 1942 w, M. FULTON 2,269,312

AUTOMATIC STOKER Filed Oct. 9, 1939 13 Sheets-Sheet 6 M. WLTQN AUTOMATIC STOKER Filed 001:. 9, 1939 l3 Sheets-Sheet 7 Wesialz NR m Tm W5 Fm M M w Jan, 13, 1942.

l3 Sheets-Sheet 8 Filed Oct. 9, 1939 Jan. 13, 13'? w. M. FULTON AUTOMATIC STOKER l3 Sheets-Sheet 9 Filed 001:. 9, 1939 Jan. M, 1942. M. FULTON 9 AUTOMATIC STOKER Filed Oct. 9. 1939 15 Sheets-Sheet 11 w. M. FULTON 2,2693% AUTOMATIC JTOKER Filed Oct. 9. 1939 15 Sheets-Sheet 13 GttornngaI 234 5 (56 I56 359 3 6 156 9 Cmmmjchwm Patented Jan. 13, 1942 AUTOMATIC STOKER Weston M. Fulton, Knoxville, Tenn., asslgnor to W. J. Savage Company, Inc., Knoxv 'le, Tenn., a corporation of Tennessee Application October 9, 1939, Serial No. 298,661

32 Claims.

This invention relates to automatic stokers for burning solid fuel, and more particularly to the cross draft" type of stoker such as that generally described and shown in my U. S. Patent No. 2,126,104 granted August 9, 1938.

Cross draft stokers of the types now known and used possess a number of objectionable features. These defects and shortcomings are due in part to the stringent requirements of the domestic field in which these stokers are widely used. Domestic stokers are required to meet conditions quite different from power plant stokers. For example, domestic stokers are used principally in the heating of residences, small apartment houses, etc., where the heating load varies with the weather and consequently is subject to very wide extremes. Noise anddust must be avoided. Further domestic stokers are cared for either by the house owner or by a domestic servant, the vast majority of whom are not familiar with mechanical devices and consequently neglect the mechanical upkeep of the stoker. Power plant stokers, on the other hand, operate under more uniform load conditions; are installed in industrial plants with other noisy machinery, need not be silent and are under the constant care of a skilled power plant engineer. Power plant stokers are usually installed at the time the power plant itself is installed, whereas the vast majority of domestic stokers are installed on heating plants of varying design that have been in service for a greater or less length of time with resulting installation difiiculties not found in the power plant stoker.

Another objection to known stokers of this type is their inability to remain idle for protracted periods of time when the load demand drops to, or near, zero, and then promptly resume normal functioning when the demand abruptly and drastically increases. When these stokers are standing idle it is necessary to admit an appreciable amount of air to the combustion zone to create a natural draft through the chimney, or smoke pipe to which the stoker is connected.\ Otherwise smoke and fumes arising from the incandescent fuel in the burner would escape around the access doors of the stoker and fill the furnace room and work their way up into the living quarters of the house being heated. This natural draft produces slow combustion of the fuel in the stoker, and, if greatly prolonged, will consumeall available fuel and the fire becomes very low. When demand is resumed and fresh fuel is fed into the stoker this fuel is consumed as fast as it is fed to the stoker and the fire has great difficulty in building up'again to normal proportions. This objection may be illustrated by reference to the shaker grate type of stoker in wide use in which fuel is discharged by gravity from the feed hopper to the shaker grate and moves slowly over the grate while being consumed. The rate of feed and rate of combustion are so timed that combustion will be completed as the moving fuel reaches the discharge end of the shaker grate. If the load demand drops and the stoker remains idle for a protracted period of time, the natural draft required to carry fumes away will consume all the fuel at the lower end of the shaker grate (this fuel having already been partially consumed), and consequently this portion of the grate will be covered with dead ash. When demand is resumed, all the cold air from the blast fan which passes through the lower portion of the grate will find no fuel with which it may combine and will mingle with the hot gases rising from the burning fuel at the upper end of the grate, cooling these gases and reducing their heating effect. Furthermore, since the rate of feed and rate of combustion are timed for normal working conditions under a fairly constant load, the feeding-device is now lacking in capacity to supply suflicient fuel for actual combustion plus a surplus sufficient to again cover the lower portion of the shaker grate. Various devices such as the so-called automatic air controls for adjusting the air supply to correspond with the thickness of the fuel bed have been produced in an effort to cure this defect in these stokers, but these devices have met with little more than indifferent success.

Another objection to known stokers of the cross draft type, to which the present invention pertains, is that they have hitherto failed to provide ready access of air to that portion of the fuel lying against the opposing wall sections of the combustion chambers. In stokers utilizing the cross draft principle the distance between the front and rear sections of the combustion chambers must be relatively small to maintain a relatively thin fire-bed, since in a thick fire-bed the temperature of combustion reaches such a high point that large, unwieldy clinkers are formed in the combustion chambers, clogging the latter and making ash disposal difficult. Hollow, water-cooled'members in close proximity to each other and in physical contact with the burning fuel have been used to rapidly conduct heat away from the fuel and prevent the temperature of the latter from rising matecharge of the ash has been possible.

rially above the fusing point of the ash. This expedient fails when the fire-bed is very thick since a region will still exist midway between the front and rear sections where high temperatures will prevail and objectionable clinkers will form. When a thin fire-bed is used the width of the front and rear sections of the combustion zone would be relatively large. Hence there are zones, or pockets in the fuel bed where the latter lies against these front and rear sections which the air cannot reach since the tendency of the air is to pursue a straight-line course through the fuel and the slight resistance to the progress of the air offered by the fuel in a relatively thin fire-bed is not sufficient to cause the air to diffuse in the burning zone. This results in uneven burning of the fuel, fusion and consequent sticking of the fuel in the pockets referred to and arching of the entire fuel bed in the combustion chambers.

Still another defect in known stokers of the cross draft type is that hitherto only gravity dis- The presence of foreign matter in the fuel has resulted in clogging the ash discharge in the absence of positive mechanical means for forcing obstruca tions out of the path of ash flow.

Another defect in known cross draft stokers is the tendency of radiant heat to escape from the incandescent fuel through the openings of the inlet tuyeres causing a substantial waste of heat. Some smoke and fumes occasionally escape through the inlet tu'yeres as well.

Another defect in known cross draft stokers, is that fine particles of incombustible matter given off from the burning fuel lodge in the passageways of the heater. This incombustible matter, known as fiy-ash, is greatly increased in quantity by the forced draft usually provided with these stokers. No satisfactory method has hitherto been devised for automatically disposing of this fly-ash."

A still further defect of the known cross draft types of stokers is that a suitable amount of fire travel between the burning fuel and the heating surface of the boiler cannot be provided. To those skilled in the art it is well known that the flame generated by burning fuel is composed of a mixture of hot gases which are rapidly undergoing chemical changes and these changes pro- ;.l

ceed to completion only after the flame has travelled a considerable distance away from the burning fuel. If these hot gases come into contact with any relatively cool surface, such as the crown sheet of a boiler, and are thereby cooled below the temperature of ignition of the component gases before combustion has been completed, chemical change will be arrested and the temperature of combustion will fall short of its maximum reducing the heating effect and wasting fuel. This is a matter of such importance that heating inspectors in many localities require that all stokers installed within their jurisdiction have a specified minimum distance between the stoker or burner and the heating surface of the boiler.

It is accordingly an object of the present invention to provide a novel cross draft type of stoker which is suitable for general requirements, particularly domestic, and which is readily adaptable for use with existing heating plants.

Another object of the present invention is to provide anovel cross draft type of stoker which can after long periods of idleness promptly resume normal operation when the heat demand is increased.

Another object of the present invention is to provide a novel cross draft type of stoker in which combustion supporting gases may reach every portion of the burning zone.

Another object of the present invention is to provide a novel cross draft type of stoker in which the formation of clinkers is reduced to a minimum.

Another object of the present invention is to provide a novel cross draft type of toker in which positive means are provided to assist the gravity discharge of ash and spent fuel to prevent arching and clogging of the ash flow.

Another and further object of the present invention is to provide a novel cross draft type of stoker in which the inlet tuyeres admit suitable gases to support combustion but prohibit the escape of radiant energy.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which means are provided for the automatic removal of entrained particles and fly-ash" from the gases of combustion.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which a suitable amount of fire travel is provided to insure complete combustion of the gases of combustion before they reach the heating surfaces.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which more fuel is supplied to the burning zones than is required for the normal operation of the stoker.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which auxiliary means are provided for removing fumes and gases generated during periods when the stoker is idling which is automatically controlled in conjunction with the dampers of the stoker.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which the cross draft is induced in rather than forced through the burning zones.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which novel means are provided for inducing the cross draft in the burning zones.

Another and still further object of the present invention is to provide a novel cross draft type of stoker in which novel means are provided for distributing the fuel to the burning zones and returning surplus fuel to the source of fuel supply.

Another and still further object of the present invention is to provide a novel cross draft type of stoker which is silent in operation, efficient, compact, relatively inexpensive to manufacture and install and which may be operated without prior knowledge or training.

Other and further objects of the present ir. vention will appear as the description thereof croceeds.

With these objects in view, illustrative embodiments of the cross draft stoker of the present invention are shown in the accompanying drawings but it is to be expressly understood that these embodiments of the present invention are shown in the accompanying drawings and hereafter described for the purposes of illustration only and are not to be construed as limitations of the present invention. Reference should be had to the appended claims to determine the scope of the present invention.

In the accompanying drawings, Fig. 1 is a front elevation of one embodiment of, the novel cross draft stoker of the present invention shown installed with a boiler of the. usual type and having a portion of the front of the stoker jacket broken away to show the front of the stoker;

Fig. 1a is a continuing view of Fig; 1 showing a front elevation of the ejector and smoke eduction passages;

' Fig. 2 is a side elevation as seen from the left of the embodiment of the present invention shown in Fig. 1;

Fig. 3 is a side elevation as seen from the right of the embodiment of the present invention shown in Fig. 1 with the boiler removed;

Fig. 4 is a view of the embodiment of the present invention shown in Fig. 1 as seen from above with the top of the jacket and the top of the fuel hopper broken away;

Fig. 25 is a sectional view of still another embodiment of the novel cross draft stokerjo'f. the present invention. 1

Referring now to the accompanying drawings in which like reference characters indicate similar parts and more particularly, to Figsl and 2, the stoker 25, made up of hollowisectionswhich will be described hereafter-: in detail is connected to the boiler 28 by means of pipes 21 and 28, in accordance with the practice'known'jto the art for stokers of this typetopermitfree exchange of water and steam betweenfgthe boiler and stoker. Combustion of fueljtakesplace in the stoker 25 and the hot products of combustion pass through the stoker outlet .23 into the ashpit 30 of boiler 23 thence upward through the heating passageways of boiler-.26 and out through Fig. 5 is a cross sectional elevation on the line 6-6 in Fig. 3 of the embodiment of the present invention shown in Fig. l;

x Fig. 7 is a sectional view on the line 1-1 of the embodiment 'of the present invention shown in Fig. 1, the electric motor and fan being omitted for clarity; i

Fig. 8 is an isometric view ofiiaa stoker side member;

Fig. 9 is an isometric view of a stoker side member opposite the side member of Fig. 8.

Fig. 10 is an isometric view of opposite outside intermediate stoker members;

Fig. 11 is an isometric view of an inside intermediate stoker member;

Fig. 12 is a cross sectional taken on the line l2- -l2 of Fig. 11;

Fig. 13 is an isometric view of a movable tuyre member with one side broken away to show the internal construction;

Fig. 14 is an isometric view of a tuyre operating frame;

Fig. 15 is an enlarged view of a part of Fig. 1 showing the spring construction for holding a tuyere member to the tuyre operating frame;

Fig. 16 is a' cross sectional elevation of another embodiment of the novel cross draft stoker of the present invention;

Fig. 1'1 is an isometric view of opposite outside the smoke-hood 3| to smoke-pipe 32. It has hitherto been the practice ,to apply forced draft to stokers of this type. In-the present invention, an induced draft is used. To create the desired induced draft an electric motor 33, supported on bracket 34 attached to stoker 25, carries the rotor 35 of a blower 36 on the end motor shaft 31. into the air intake 39 of ejector 40 which is in communication through chamber 5| with suction chamber 42. Pipe 4| is connected to said suction section 42 of ejector 40 and the gases are delivered through pipe 32 to any suitable chimney or stack (not shown). Motor shaft 31 has pulley 43 keyed thereon and belt 44 transmits power from pulley 43 to pulley 45 which is keyed to shaft 46 of speed reducer 41 of any standard construction.

Referring more particularly now to Figs. 1 and 2, fuel hopper 60 is provided with lid 61 hinged at 82 and provided with a handle 63. A metal jacket, or covering, 84 surrounds stoker 25 and extends to the bottom 85 thereof to form a substantially air-tight closure around stoker 25. At

the top of jacket 64, and in communication with the interior thereof, is vent pipe 66. Pipe 66 leads to any suitable outlet such as the chimney used with boiler 26; it may connect to ash pit 30 of boiler 26; or, as here shown, it may connect at 61 to smoke pipe 32. Jacket 64 has adjacent intermediate members used with the embodiment of the present invention shown in Fig. 16;

Fig. 18 is a more detailed view of a part of Fig. 16 showing a portion of an upper and a lower tuyere member when separated as seen from the front;

Fig. 19 is a sectional view on the line l9+ll of Fig. 18;

Fig. 20 is a sectional view of a portion of an upper and a lower tuyere member when in closed position;

Fig. 21 is an isometric view of a modified tuyre member suitable for use with the embodiment of the present invention shown in Figs. 1 and 16;

Fig. 22 is a cross sectional elevation of another embodiment of the novel cross draft stoker of the present invention;

Fig. 23 is a cross sectional view of a portion of the novel cross draft stoker of the present invention showing another embodiment of the side sections and tuyre members;

Fig. 24 is a cross sectional view of a portion of the novel cross draft stoker of the present invention showing still another embodiment of the side sections and tuyre members; and

its top, and immediately above combustion chambers 68 (Fig. 5), two openings 69, which are provided with lids 10 hinged at 1| and provided with handle 12. Handle 12 has a round ei'ite sion 13 journalled in lug 14 integral with li Extension 13 carries latch 15 which, whendid 10 is closed, can be rotated to'engage reinforcing member 80. Each lid HI is opened by rotating handle 12 to disengage latch 15 and lid 10 can then be raised to the open position shown in dotted outline at the left in Fig.6. This arrangement permits access to combustion chambers 68 for starting the fire in the stokerand gives access to the working parts.

Connected to air duct 33, and in communication with the interior thereof, is pipe 8| which takes .air under pressure from duct'38 to any suitable pressure responsive device 82 here shown as comprising a cast iron housing 33 inclosing bellows member 84 having a plunger 85 attached to its movable wall. Plunger 85 pivotally engages member 81 which in turn is mounted upon pivot 83 and carries a lever arm 89. Pressure responsive device 82 is supported in any suitable way here shown as by bracket so suitably secured to jacket 64 as by screws or rivets 9|.

5 Mounted in vent pipe 65 is damper 92 supported Blower 36 discharges air through pipe 33 on pivot 33 to which is secured operating arm 94. Arm 94 pivotally engages link 05 which is in turn in pivotal engagement with lever arm 03 of th pressure responsive device 32.

Referring now to Figs. 3. 4, 5 and 7, in communication with air duct 34 is pipe 90 communicating in turn with branch pipes 91 and 90 leading to suitable pressure responsive devices 90 and I00, here shown as of similar construction to pressure responsive device 02. Pressure responsive devices 99 and I are provided with plungers I02, pivotally connected at I03 to damper arms I04. Pressure responsive devices 99 and I00 are attached to stoker 25 by brackets I05. Suitable dampers I05 are mounted in housings Ill provided with flanged portions I03, by which housings III! are suitably secured to Jacket 64 by screws, rivets or other suitable means. Housings I01 enclose suitable openings I09 (Fig.

5) which are provided in Jacket 04 for the admission of air to support combustion in stoker 25. Dampers I04 are provided with trunnions IIO which are mounted in the ends of housings I01 for rotation therein. Damper arms I04 are secured to one end of trunnions IIII to enable pressure responsive devices 99 and I00 to operate dampers I05.

Referring now to Figs. 1 to 12, inclusive, it will be seen that the combustion chambers 53 of my improved stoker are built up of a plurality of hoilow sections spaced from each other and secured together by a plurality of hollow nipples which are screwed into suitable threaded bosses or openings in each section. As shown in Fig. '7.

hollow side sections III and H2 (Figs. 8 and 9) have mounted therebetween one or more hollow outside sections II3 (Fig. 10) and an equal number of inside hollow sections II4 (Fig. 11). Combustion takes place in the combustion chambers 59, inclosed by side sections III and H2, outside sections II3 and inside sections 4, and the hot gases from the burning fuel pass out through the central chamber II5 formed by inside sections II4. Outside sections II3 are identical in construction having their lower portions IIl downwardly and inwardly inclined towards the middle of the burner so that lower portions 1 are closer at their lower extremities than at their upper extremities. Referring to Fig. 12, inside sections II4 are hol low to provide passages H9 through which water can freely circulate. Inside sections II4 have ribs H9 formed integrally therewith the spaces I between ribs II9 constituting tuyres through which the hot gases of combustion enter central chamber H6. Side sections III and H2;

have ribs I formed integrally therewith having spaces I25 therebetween which when assembled form companion tuyeres with those formed by the inside sections II4.

Side section III has therein a suitable opening I21 surrounded by extension I20 into which is fitted a suitable member I29 suitably secured thereto, by any convenient means here shown as by screws I30, and extending into chamber II6. Member I29 forms an outlet through which the gaseous products of combustion pass in their travel to boiler 26. Member I29 may be made of any suitable heat-resisting material such as fireclay or any of the heat-resisting alloys. Member I29 is so designed that the hot gases of combustion emerging from tuyeres I20 nearest opening I21 must travel to the opposite side of stoker 25 before escaping through open end I3I of member I29 to giv the gaseous products of com- 75 bastion a long path of travel and ample time in which the chemical reactions of combustion may be completed before the gaseous products of combustion come into contact with the relatively cool interior passageways of boiler 23. As member I29 is exposed to the hot gases of combustion emerging from tuyeres I23 its outer and inner surfaces are maintained at high temperatures. The gases in contact with and surrounded by these surfaces will therefore be held at a temperature above the temperature of ignition of the component elements of the gases until they emerge from opening I21. Adequate i'ire travel to insure complete combustion is thus provided by the present invention.

Inside sections II4 are V-shaped in cross section (Figs. 7 and 11) with the top of the v pointing towards combustion chambers 40. .Outside sections III are also V-shaped with the top of the V pointed towards combustion chambers 03. Sections II3 have no tuyere forming ribs. Hollow hubs I32 (Fig. 10) formed on sections II3 project a suilicient distance beyond the sides of sections I I3 to form suitable spaces therebetween in which oscillating tuyere members I33 (Figs. 5. 7 and 13) are mounted for reciprocation. As shown in Fig. 13 tuyere members I33 comprise two side elements I34 and I35 having cooperating ribs I39 and I3! suitably lapped at I33 and I to form a fuel-tight joint. These joints provide any adjustment necessary to counteract expansion and contraction of ribs I33 and I31 caused by their exposure to heat and also provide an adjustment for wear. When tuyere side elements I34 and I are assembled a tuyere structure is formed which is generally V-shaped in cross section tofit snugly in the spaces between the sides of. v-shaped outside sections H3 and of sufficient thickness to extend inwardly beyond sections II3 into contact with the burning fuel in combustion chambers 03. Tuyere elements I34 and I35 are apertured at I40 (Figs. 5 and 13) to carry rods I which in turn carry links I42 pivotally mounted thereon. Tuyere elements I34 and I35 are also apertured at I43 to carry rods I44 which in turn carry links I45 pivotally mounted thereon. Each one of ribs I36 and I31 of tuyere elements I34 and I35 is composed of an upwardly inclined portion I44 and a downwardly inclined portion I4'I. Air entering combustion chambers 58 through tuyeres I33 is therefore forced to first travel upwardly and then downwardly. The outer upwardly inclined portions I46 act as baiiies tointercept the rays of radiant heat which would otherwise escape from the incandescent fuel in chambers 68. This radiant heat arrested by upwardly in clined portions I46 is absorbed by the relatively cold entering air as it impinges against these surfaces and is thus returned to the burning fuel to add to its heating eifect. The downwardly inclined portions I41 act to prevent fuel from entler'ing and passing outwardly through tuyeres Referring now to Figs. 8 and 9, the flat faces I48 of side sections I II and H2 are provided with T-shaped lugs I49. A suitable rectangular frame I (Figs. 1, 5, 7 and 14) has slots I5I designed to engage lugs I49. Fig. 14 is an isometric view of frame I50. Slots I5I are enlarged at I52 to permit the T-heads of lugs I49 to pass therethrovgh. When frame I50 is moved downwardly the sides of slot I5I pass beneath the T-heads while the smaller body portions of lugs I45 fit in slots I5I. The reduced portions of slots I5I are of suitable length to allow frame I50 to oscillate within its required range of movement without the T-heads of lugs I48 entering openings I52. Lugs I49 serve to guide frame I50 in true rectilinear movement and to retain it in sliding contact with faces I48 of sections III and H2. Frame I50 has also therein rectangular openings I53. Arranged on each side of upper openings I53 are suitably formed prong members I54 and I55 which project perpendicularly from the rear surface of frame I50. Fig. 15 is an isometric view of a portion of frame I50 showing the arrangement of the several parts when frame I50 is in operating position as shown in Figs. 1, and 7. Suitable resilient strips I56 are suitably secured to frame I50 as by screws or rivets I51, and are so arranged that ends I58 of strips I56 pass through suitable openings I59 in the outer ends of links I42 which are designed to protrude through openings I53. As described above, the inner ends of links I42 pivotally engage rods I which in turn engage tuyere members I33. The force exerted by strips I55 therefore acts to draw tuyere members I33 snugly into the spaces between outside sections II3. A firm contact between tuyre members I33 and the side surfaces of outside sections H3 is insured. Any wear of the contacting surfaces will be taken up by strips I56. The firm contact between tuyeres I33 and sections II3 enables hollow water cooled sections II3 to conduct heat away from tuyre members I33 at a sufilpiently rapid rate to prevent the latter i'rom becoming overheated and permanently damaged.

Prong members I54 and I55 straddle links I42 and engage rods MI between their upper and lower prongs. Lower openings I53 of frame I50 correspond in number and are correspondingly arranged to openings I53 in the upper portion of frame I 50 and are provided with similar springs or strips I56 (Fig. 1) engaging the outer ends of links .I45 to draw the lower ends of tuyre members I33 snugly into place between stoker sections I I3 to insure continuous contact between the side walls of sections H3 and tuyre members I33 throughout the entire length of the latter. Lower openings I53 are not provided with prong members corresponding to members I54 and I55 since the latter are sufficient to impart movement to tuyeres I33. When frame I58 is reciproeated, as will be hereafter described, a like movement is imparted to tuyere members I83.

Secured to frame I50 are bifurcated lugs I80 projecting therefrom. Pivotally mounted in bii'urcated lugs I60 on pins I5I are links I52 which are longitudinally slotted at I53 for engagement with pins I5I. Links I52 have mounted therein and extending into slots I53 screws I64 whose diameter is approximately equal to the width of slots I88 to provide regulation of the effective length of slots I63. Links I52 are pivoted at I65 to rods I65 which in turn engage lower tuyere members I81. Lower tuyere members I81 slidably engage and rest upon the sides of the lower inwardly inclined portions II! of sections H8 and are held in contact therewith by their own weight plus the weight of fuel resting upon them. Spaces I58 (Fig. 5) between the lower end of tuyeres I33 and the upper end of tuyeres I61 are bridged by plates I59 hinged at I to the bottom of tuyeres I33, and having their lower ends slidably engaging the upper portion of tuyeres I51. Plates I69 are designed to bridge spaces I68 during reciprocation oi tuyeres I33 and I61.

Referring more particularly to Figs. 5, 8 and 9, formed adjacent the lower ends of side sections III and H2 are plates I'II. Plates "I are provided with offsets I12 having extensions I13. Also formed on sections III and H2 are lugs I14 designed to receive plates I15 positioned between sections III andII2, plates I15 having their upper ends supported by lugs I14 and their lower ends supported in offset I12. Plates I15 catch any dust or ash which may sift through tuyeres I33 and direct this waste 'matter downward into the ash discharge. Suitably secured to plates I1I are curved plates I16 which close the space between sections III and H2 and extend forwardly to a point adjacent the front of the stoker. Plates I16 deflect the ash traveling downward from combustion chambers 68 into opening I11 of a suitable ashpit I18. Plates I16 are here shown secured to the left sides (Fig. 5) of sections III and H2 but it is to be understood that plates I16 can be connected at the right if desired. Ashpit I18 would then be located near the left side of Fig. 5 this feature rendering installation of the stoker more flexible.

As is best seen in Figs. 5 and 6, a suitable member I19 is spaced from and covers the top of stoker sections II4 providing a suitable space I around it in which scrapers I8I may move with ample clearance. Member I19 prevents fuel from accumulating in the space on top of stoker sections II4.

Stoker side section II I is provided with a hollow, water-cooled outlet 29 (Figs. 3, 6 and '1) for conducting the hot gaseous products of combustion from outlet I21 and member I29 into boiler 26. Outlet 29 is of suitable cross section here shown as rectangular and is downwardly directed to deliver the hot gases of combustion at, or near, the bottom of boiler 26, as may be seen in Fig. 1. Outlet 29 has vertically disposed ribs I84 and I suitably secured to opposite walls I82 and I83 to which are attached cross members I85 and I81 forming dust-collecting passages I88 and I89 therebetween. Cross members I85 and I81 have their upper edges turned outwardly towards the center of outlet 29 and are suitably separated from each other to form traps by which fly-ash and dust particles may enter passages I88 and I89. Passages I88 empty into a.

suitable passage I90 which in turn empties into dust-collecting chamber I9I. Passages I 89 are divided at I92 into two branches I93 (Fig. 3) which straddle outlet 88 and discharge into dust chamber I9I. A suitable passage I98 connects dust chamber IQI and outlet 29. The area of passage I88 is greater than the area of passage I80. When induced suction or draft is applied to outlet 29 through boiler Eli to which it is connecmd, gases can escape from dust chamber I8I through passage I88 faster than they can enter through passage I88 producing a reduced pressure inside chamber I8I. Mounted in chamber I9I is conveyor screw I85 journalled at I96 in wall I81 of chamber ItI and having its discharge end I98 loosely mounted in a suitable cylindrical hub I98 opening into ash discharge passage 200. End I98 of screw I05 terminates short of the entrance of hub I89 into ash discharge passage 200 to permit a suitable quantity of dust or flyash to accumulate in hub I88 to form a seal or plug to prevent air from being drawn into chamber I9I through ash discharge 200. As will be described hereafter in more detail, a ratchet wheel 2|3 is secured to screw I36 and is positioned between the bifurcations of lever 2H and is engaged by pawl 2|2 secured to lever 2| I.

Referring now to Figs. 1-8, 14 and more particularly Fig. 3. speed reducer 41 has a suitable reduced speed shaft 233. on which is mounted a suitable cam 2|4 provided with a cam groove 2|6. Rod 2|6 mounted for reciprocation in brackets 2II has rotatably mounted thereon a suitable roller 2| 3 designed to engage and travel in cam groove 2I5. Rod 2l6 pivotally engages arm 2I3 of crank 223. Pivotally engaging arm 2|3 of crank 223 is rod 22| which in turn pivotally engages arm 222 of crank 223. Crank 223 is fixed to shaft 224 which is iournal1ed,in bracket 226 attached to stoker 25. Crank 223 is fixed to shaft 226 which is Journalled in bracket 221 also attached to stoker 25. Shaft 224 has fixed thereto crank arm 223. Pivotally engaging arm 223 is rod 223 which in turn pivotally engages lever 2 above described. As above described lever 2 is bifurcated at its opposite end and the bifurcations are loosely journalled on screw I35. Between the bifurcations, and fixed to screw I35, is ratchet wheel 2) whose teeth are engaged by pawl 2I2 urged into engagement with ratchet wheel 2I3 by spring 233. Bearings23| (Figs. 8

and 9) are provided in side sections III and 2 to support shafts 224 and 226. Shafts 224 and 226 extend across from stoker side section III to side section H2 and are suitably spaced from the outer edges of intermediate sections II3. Fixed to shafts 224 and 226 are crank arms 232 and 233 (Fig. 5) which pivotally engage rods 234 and 235 which in turn pivotally engage bifurcated lugs 236 (Fig. 14) of frame member I63.

Referring to Figs. 4, 5 and 6, a second reduced speed shaft 2|3 of speed reducer 41 passes through jacket 64 and is iournalled in bracket 231 fixed to top member 236 of fuel hopper 63. Suitable packing means may be used to insure a gastight joint where shaft 2|3 passes through jacket 64. Secured to shaft 2|3 is bevel pinion 243 which meshes with pinion 24l fixed to drive shaft 242 of conveyor screw 243. Spur gear 244 likewise fixed to conveyor shaft 242 meshes with idler gear 245 which in turn. meshes with spur gears 246 and 241. Gear 246 is fixed to drive shaft 243 of secondary conveyor screw 243. The general construction and operation of conveyor screws 243 and 243 here shown and generally described is the same as that shown and described in detail in my copending application Serial No. 263,930, filed January 31, 1939, for Improvements in feeders. has four arms 26I secured to the lugs 262 formed on side sections I'll and 2. Fixed to spider frame 263 are studs 263 to which are lournalled sprockets 264 and 265. Spur gear 241 is fixed to shaft 266 which rotates in its stud 263 and carries sprocket 264 fixed thereto. The other sprockets 265 turn idly on their studs 263. Sprocket 264 drives sprocket chain 261 and sprockets 265 support and stretch chain 261. Chain 261 carries a plurality of scrapers I3I pendant therefrom.

As is well known to those skilled in the art to which this invention pertains, stokers of this type are controlled by an electric switch in turn controlled by any convenient means such as a thermostat located in the building being heated. Assuming that the temperature in the region of the thermostat has fallen sufliciently to close the electric switch and admit electricity to motor 33, the latter will rotate blower 36 and supply air A spider frame 263 to duct 33 at a pressure above atmospheric pressure. Pipes 3|, 33, 31 and 33 will conduct air under pressure to pressure responsive devices 32, 33 and Ill, compacting the bellows and moving plungers 36 and I32 outward. Outward movement of plunger 36 will rotate rocker 31 about pivot 33 and rotate lever 33 and move link 36 downward rotating damper 32 to the dotted position shown in Fig. 1 obstructing the flow of gases through vent pipe 63. Vent pipe 63 carries away from jacket 64 all gases, smoke, fumes, etc., which may escape from stoker 25 only while the latter is idle. Simultaneously pressure responsive devices 33 and I33 will rotate dampers I36, to the dotted positions shown in Fig. 5 to admit air to assist combustion in the stoker. As soon as the temperature in the region of the thermostat has risen suiflciently to cause the thermostat to open the electric circuit motor 33 will cease driving blower 36 and the pressure in pressure responsive devices 32, 33 and I33 will drop. The resilient walls of the bellows members will expand them to their normal positions rotating damper 32 to its open position and rotating dampers I36 to their closed positions. Free flow of gases will now take place through vent 66, and no air will be admitted through openings I33 to support combustion. .This novel method of handling the air for combustion and the escaping fumes of a stoker accomplishes the very desirable result of preventing the escape of noxious fumes in the boiler room (which is always objectionable and. in the case of residences, is prohibitive), and, at the same time, automatically provides air for combustion when the stoker solid fuel) is supplied with a shovel until chambers 63 have been filled up to the level of the lower edges of scraper I3I. Lids 13 are then closed and secured by turning handles 12 to rotate latches 15 into engagement with members 33. Electric motor 33 is then started putting blower 36 into operation and closing damper 32 in vent pipe 66 and opening dampers I36 in the lower sides of jacket 64. The air supplied through air duct 33 from blower 36 to ejector 43 produces an induced draft or suction in smoke-hood 3|, in boiler 26 and in stoker 26 causing air to be drawn in through damper openings I33, through tuyeres I33 through the burning fuel in chambers 63, and causing the hot gases of combustion to be drawn through tuyeres I26 through cylindrical member I23 and through outlet member 23 into boiler 26 as indicated by arrows in Figs. 5, 6 and 7. This vigorous indraft of air through the stoker causes the fuel in combustion chambers 33 to ignite rapidly until combustion is taking place throughout combustion chambers 63 up to the zones indicated by dotted lines 213 (Fig. 5). As there are no inlet and outlet tuyeres above the zones indicated by lines 213 the fuel in this space receives insufilcient air to support combustion. Particles of dust, or fly-ash," that may be held in suspension in the hot gaseous products of combustion are thrown out of the gaseous stream in turning the reverse curve in outlet member 28 at high velocity by the action of centrifugal force and are caught by the outwardly protrudlng edges of cross members I86 and I81 and deflected through the passages between these cross members into the passages I88 and I88. The reduced pressure in dust chamber I8I causes the particles thus trapped to be drawn or sucked through passages I88 and I88 into dust chamber I8I. At the same time that electric motor 88 starts blower 86 it drives pulley 45 of speed reducer 41 through belt 44 driven by pulley 48 secured to motor shaft 81. Reduced speed shaft 288 (Fig. 3) is rotated, rotating earn 2 and imparting rectilinear reciprocating movement to rod 2I6 whichin turn oscillates crank 228 and, through rod 22I, likewise oscillates crank 228. Oscillation of cranks 228 and 228 rocks shafts 224 and 226 oscillating cranks 282 and 288. Oscillation of cranks 282 and 288 reciprocates connecting rods 284 and 285 reciprocating frame I58. Reciprocation of frame I58 reciprocates tuyere members I88 through engagement of rods MI and prong members I54 and I55. Simultaneously pins I6I carried by bifurcated lugs I68 acting against the upper and lower limits of slots I68 in links I62 cause lower tuyere members I61 to reciprocate. The length of stroke of tuyere members I61 is regulated by adjusting screws I64. When screws I64 are turned inward to reduce the effective length of slots I68 the amount of lost motion permitted pins I6I is reduced and the length of stroke of lower tuyere members I61 is correspondingly increased. Turning screws I64 outward increases the lost motion and decreases the length of stroke of lower 'tuyere members I61.

Reciprocation of tuyeres I88 produces many desirable results heretofore not obtained. It agitates the fuel in combustion chambers 68 breaking up arching, prevents formation of holes in the fuel bed due to "burning through and works the fuel downward in combustion chambers 68. Reciprocation of tuyeres I88 also produces a better distribution of air entering the fuel bed by constantly moving the tuyre open- -1 ings to different positions relative to the fuel. As the fuel is worked downward in chambers 68 and combustion proceeds the fuel is reduced to ashes and its volume is reduced. Because of this reduction in volume the rate of movement of the contents of combustion chambers 68 must decrease towards the bottom of chambers 68. To accomplish this reduced rate of movement of the fuel lower tuyres I61 are provided with the lost motion attachment above described so that they may be adjusted toreciprocate through a shorter distance than upper tuyeres I88. Lower tuyres I61 terminate at their lower ends in ribs 21I which act to push, or kick," the ashes from combustion chambers 68 into the ash discharge outlet 288. The ashes are thus positively ejected from the burner and may be disposed of in any way desired such as shown by allowing them to fall through an opening I11 into a suitable ashpit I18. Screws I64 afford an adjustment for the amplitude of rec'procation of tuyeres I61 and so also for ribs 21I thus providing an adjustment for the rate of discharge of the ashes. v

Because stoker sections I88 are V-shaped in cross section the incoming air in passing through tuyeres I88 which are likewise V-shaped in cross section is allowed to spread laterally before it reaches the fuel in combustion chambers 68. The V-shaped cross section of center stoker sections II4 allows the gaseous products of combustion to converge after passing through the fuel in combustion chambers 68 before entering chamber II6. Air is therefore conducted to every portion of the burning fuel in chambers 68 preventing the formation of pockets of unburnt fuel and increasing the ei'iiciency of the stoker.

Reciprocating movement of rod 2I6 imparts oscillating movement to crank arm 228 and through it reciprocates rod 228 and oscillates lever 2II causing the latter to slowly rotate ratchet wheel 2I8 rotating conveyor screw I85 to discharge fly-ash from chamber I8I into ash discharge 288. Automatic disposal of dust and fly-ash is therefore provided.

Simultaneously with the operations just described, reduced speed shaft 2I8 (Fig. 6) rotates bevel pinions 248 and 2 and rotates conveyor screws 248 and 248 which in turn elevate fuel from hopper 68 and discharge it into the space I88 at the top of the stoker. This fuel is then picked up by scrapers I8I .and distributed uniformly around the space I88, scrapers I8I being driven by sprocket chain 261, sprocket wheel 264, and gear wheels 244, 245 and 246. The speed of shaft 2I8 is so adjusted with respect to the gear ratios that conveyor screws 243 and 248 will supply fuel to stoker 25 faster than stoker 25 can consume it. The surplus fuel not consumed is carried around space I88 by scrapers I8I and discharged over wall 886 (Fig. 4) back into the hopper 68. When the stoker of the present invention remains idle for prolonged periods of time the fuel in space I88, above the dotted lines 218, serves as a reserve to replenish the fuel consumed by the slow combustion in combustion chambers 66 resulting from natural draft, and as this reserve is slowly consumed the fuel level in space I88 drops down towards dotted lines 218. When demand for heat is resumed and the stoker is again put into operation conveyor screws 248 and 248 supply fuel faster than it can be consumed and space I88 is quickly refilled and the fuel level is brought back up to the bottom edges of scrapers till, after which the surplus fuel is again discharged back into hopper 68.

as described. It is to be understood that while in the preferred embodiment of the present invention the surplus fuel is returned to the hopper it may be disposed of in any other way desired as for example by discharging it into a separate bin, or hopper, provided for that purpose.

Fig. 1'7 shows a modified form of outside stoker sections H8. it will be noted that the outside stoker sections N8 of Fig. 17 differ from those of Fig. 10 in that the V-shaped surfaces of the sections of Fig. 17 are struck on a radius 50 that they are arcuate in form instead ofhaving the lower portions H1 (Fig. 10) turned inwardly, at an abrupt angle. Fig. 16 is a cross sectional view of the stoker showing the appearance of sections H8 shown in Fig. 17 when assembled. When sections N8 of Fig. 16 are used. upper tuyere members I88 and lower tuyre members I61 are struck on the arc of a cicrle to conform to the stoker sections and operate in a manner similar to that described with reference to Fig. 5, lower tuyre members I61 being adjusted to reciprocate through smaller amplitudes than tuyre members I88.

-Referring to Figs. 18 and 19, when upper tuyere members I88 are at their maximum upper limits of oscillation and adjusting screws I64 are Comparing Fig. 17 with Fig. 10, 

